The invention relates to a touch panel control device for acoustic equipment.
Acoustic entertainment devices for vehicles, such as a cassette tape player, compact disk player and radio tuner are installed in a considerably small space such as an in-dash console, and therefore must be small in size. Accordingly, the switches or push-buttons of the acoustic devices must also be small. These small switches or push-buttons are difficult to operate. Furthermore, the acoustic devices are used in different modes and operated in various manners. Therefore they employ a variety of switches, push-buttons, etc. Since the operator cannot easily locate them while driving, his attention to the road may be distracted when operating the acoustic devices causing a dangerous condition.
In this connection, a method has been disclosed in Japanese Patent Application (OPI) No. 89720/1986 (the term "OPI" as used herein means an "unexamined published application") in which instead of switches or push-buttons for operating acoustic devices, there is provided a touch panel, the different controls of the devices being effected by touching different positions on the touch panel.
The conventional touch panel method will be described with reference to FIG. 1. A touch panel 80 having interior detecting electrodes is scanned with a scanner 20 to detect when and at what point the touch panel 80 has been touched. The detection output data of the scanner 20 are applied to a first memory 30, where the detection output data of a scan are temporarily stored. The detection output data of one scan read out of the the first memory 30 are supplied to a recognizing block 40. A touch on the touch panel is pattern-recognized by the recognizing block 40 for each scan of the scanner 20.
The output pattern data of the recognizing block 40 are applied to a second memory 50 and a data comparator 60. The second memory 50 temporarily stores the recognized pattern data produced during one scan and supplied thereto from the recognizing block 40. The data comparator 60 compares the output pattern data of the recognizing block with the pattern data of the preceding scan read out of the second memory 50, to thereby detect any change in the pattern data. The comparison output data of the data comparator 60 is supplied to a decision block 70 which outputs control data corresponding to the comparison output data. In response to the comparison output data, the decision block 70 refers to a data table (not shown) and outputs predetermined control data according to the touch on the touch panel 80.
As is apparent from the above description, in the conventional touch panel control device, the touch data of the present scan is merely compared with that of the preceding scan. Therefore, if the scanning speed is increased, the control device may judge no change in the touch position between two successive scans because the distance the finger can move over a scanning period is related to the scanning speed. lf, on the other hand, the scanning speed is decreased, the following error may be encountered. If a finger finely touches and is removed from the panel and the part of the panel touched has not yet been scanned (for instance the right part of the panel in the case of scanning the panel in the left-to-right direction), then that touch on the panel may not be detected.
Preferably, the entire panel surface should be scanned in about 10 msec to prevent a detection miss. However, if the scanning speed is set to about 10 msec, there may be an erroneous detection because, as mentioned herein before, finger speed cannot follow a rapid scanning speed.